Lifetime and Reliability Analysis of Electromagnetic Relays in UPS-AVR Systems

This paper presents a lifetime estimation for a 12V general purpose electromagnetic relay, commonly used in industrial and automotive applications, and widely employed in uninterruptible power supply (UPS) systems to perform the Automatic Voltage Regulator (AVR) process. This analysis is based on the FIDES Guide methodology, which provides a framework to calculate the failure rate of mechanical, electromechanical, and electronic components. In this work, a commercial line-interactive UPS product is used as a case study for the analysis. In addition, three potential scenarios for the AVR are evaluated, each influencing the number of relay switching operations required to regulate the output voltage. The analysis performed for Scenario 1 demonstrates that the reliability of the electromagnetic relays which are part of the UPS AVR is influenced by multiple interdependent factors. In addition, the step-time control algorithm has a significant impact on both the operational performance and the long-term durability of the relays. Therefore, the power converter designer is faced with a critical trade-off: determining an appropriate control step time and voltage regulation strategy that not only ensures stable and periodic voltage regulation but also avoids a substantial increase in relay failure rates during the first year of operation.